Stability Study of a New Compounded Medicine for the Treatment of Oral Mucositis

Oral mucositis is an inflammatory and ulcerative disease that affects patients undergoing cancer treatment, namely chemotherapy and radiotherapy, significantly compromising their quality of life. Despite its high incidence and clinical impact, current therapeutic options remain limited, reinforcing the need for new treatment approaches. In this context, the Instituto Português de Oncologia do Porto FG, EPE (IPO-Porto) developed an innovative mouthwash containing dexamethasone sodium phosphate (DSP), ascorbic acid, and sodium hyaluronate. In this work the physicochemical stability of this formulation was evaluated to ensure its quality and safety as compounded medicine. Exploratory studies were performed under accelerated aging conditions (40 ± 2 °C), followed by stability studies under real-time conditions (20 ± 2 °C) and refrigeration conditions (4 ± 2 °C), as well as in-use stability studies simulating daily patient handling. At each sampling time, physicochemical characterization was carried out (pH, color, odor, and precipitate formation) as well as the DSP quantification using high-performance liquid chromatography. The acceptable range of 90.0–110.0%, compared to the initial concentration of DSP, was used as the primary stability criterion. Results showed that the formulation remained stable at high temperatures (40 °C), on short exposures times (≤6 h), and for 30 days at 4 °C in closed amber glass bottles. In-use stability studies performed during the 7 days after opening (considering three daily applications) showed that the DSP concentration remained above 90%. The results obtained enabled us to establish a definition of storage conditions and beyond-use recommendations, since they showed that the prepared formulation is stable when stored under refrigeration. Further studies are currently being developed with a view to its clinical use as a compounded mouthwash in a hospital setting for the treatment of oral mucositis.